


Unexplainable Chemistry

by 5Lifelines



Series: TsukaSen Is My Religion [6]
Category: Dr. STONE (Anime), Dr. STONE (Manga)
Genre: Alternate Universe - High School, Alternate Universe - Modern Setting, Discord: The Kingdom of Shipping (Dr. STONE), First Time, Friends to Lovers, Friendship, Gift Exchange, High School, M/M, Modern Era, Senkuu gets what he wants, TKS, TKSChristmasInJuly2020, TKSevents, TheKingdomofShipping, Tsukasen, hs!Senkuu, hs!Tsukasa, intended for mature audiences only, read the tags and avoid content that triggers you im begging :|, they became friends in high school, this content is not for children - seriously if you're under 18 gtfo, tsukasa's pov
Language: English
Status: Completed
Published: 2020-08-01
Updated: 2020-08-01
Packaged: 2021-03-06 00:34:33
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,457
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25644382
Author URL: https://archiveofourown.org/users/5Lifelines/pseuds/5Lifelines
Summary: It wasn’t often, if ever, that Tsukasa and Senkuu had the chance to spend time alone together. However, things were about to change in a way that Tsukasa didn’t expect.
Relationships: Ishigami Senkuu/Shishiou Tsukasa
Series: TsukaSen Is My Religion [6]
Series URL: https://archiveofourown.org/series/1581793
Comments: 2
Kudos: 54
Collections: 2020 TKS Christmas in July – Gift Exchange





	Unexplainable Chemistry

**Author's Note:**

  * For [Dainonico](https://archiveofourown.org/users/Dainonico/gifts).



> A gift for Dai, for the TKS Christmas In July (2020) event! I hope that you like it!

The afternoon sun streaked through each of the lab’s windows and reflected off the many beakers and tubes that were lined across the table. A certain scientist’s green hair stood out far too much against the warm colors that filled the environment and the confident - borderline smug - smirk that he often wore. Taiju and Yuzuriha were busy staring at the boiling liquid that Senkuu was heating over the bunsen burner, both of them enamoured by the mysteriously shifting color with each bubble that burst at the surface. Tsukasa stood at the doorway, watching from a distance.

The Ultimate Primate knew that he wouldn’t completely understand the science that seemed to be behind this experiment anyways, so he didn’t have to be close enough to be in the range of a possible explosion. For a long time, his understanding of science was that it was a tool for those in power to oppress the ignorant. As such, while he greatly enjoyed Senkuu’s company, he found himself not immersing himself in Senkuu’s projects. At least, not as much as Taiju and Yuzuriha.

The sound of something sizzling at the table backed up his assertion that he shouldn’t be up close with them. Taiju appeared to be panicking while Yuzuriha giggled with playful glee, all while Senkuu maintained that smirk - clearly enjoying himself. Perhaps the most appealing thing about this eccentric scientist was his passion, though his intentions for his science was also admirable. In Tsukasa’s eyes, if the world reverted to some kind of primitive land where nature has returned to its prime, Senkuu would either be his most reliable ally or his worst enemy.

Thankfully, that was something he wouldn’t ever have to worry about.

While Tsukasa played with the idea of something as ludicrous as an alternate universe, Senkuu had found his way over to Tsukasa and he’d put on a much more devious grin. Tsukasa lifted an eyebrow, filled with intrigue. He couldn’t quite tell what Senkuu had in mind at the moment, but - if anything was clear - it was that the green haired scientist would make his intentions clear momentarily.

“Is there something that I can assist you with, Senkuu? You already know that I don’t usually participate in your experiments.”

Senkuu merely shrugged and pat Tsukasa on the shoulder. The firm action was counterbalanced by his apparent frailty. Thinking about it a little more critically, some would think that the two of them were some kind of mis-matched pair. What did a professional martial artist and a genius scientist have in common? As if on cue, Senkuu replied to Tsukasa’s question while also seeming to answer his thoughts.

“Not really. I just like having you around. After all, who can beat the kind of passion we have in our fields? Though hanging around only in school is a little boring. Why don’t you stop at my place after we get out of here and we can have deeper conversations without having to deal with Taiju and Yuzuriha getting lost in what we’re saying?”

Tsukasa wasn’t completely against that idea. The four of them spent a lot of time together - at least when Tsukasa wasn’t training and Senkuu wasn’t addressing a new experiment. A pair rather than a quartet would have been a nice change of pace. Shrugging casually, Tsukasa put on his own smile and nodded.

“Why not? If you’re done here, we can just head out now and leave the lovebirds to their own devices.”

Taiju and Yuzuriha seemed to have overheard that comment - not that Tsukasa was saying it quietly or secretly - and the two of them flushed with embarrassment. The two of them seemed to pick up the vibes that Tsukasa and Senkuu were putting down and saw themselves out of the room and on their way home. Senkuu took the time to pack up the equipment that he was working with while Tsukasa waited patiently outside the door, pondering what he’d discuss with Senkuu.

It didn’t take long for the scientist to meet the martial artist and they both went down the stairs and out the doors of the school building. A teacher waved them both on their way and the two of them headed over to Senkuu’s home. A good portion of their walk involved talking about Taiju and Yuzuriha, how Tsukasa’s training was going, the details of Senkuu’s experiments. Overall, it was the ramblings of two people who would hang around a good portion of the time, but who were bad at holding conversations due to their lacking similarities.

By the time they had realized it, though, Tsukasa was at the steps to Senkuu’s apartment complex and was about to wave and be on his way home. Though, before Tsukasa could make any moves towards leaving…

“Hey, why don’t you come in? I’ve got some leftovers for dinner that are far too much for me to eat on my own.”

While Tsukasa tended to stick to a strict diet to keep his stamina and figure, he also found it hard to deny a friend’s invitation to join them for a meal. Something like a warrior’s pride beckoned him to nod his head in agreement.

“I’ll take you up on that. You live alone, don’t you?”

“Yeah. Byakuya - sorry, my father just recently started working overseas, so I'm still used to preparing for two.”

“Ah, then that makes sense. Please, lead the way.”

Half an hour later, the two of them had eaten a decently sized meal of rice, steamed salmon, a light miso, and a pairing of pickled vegetables that Senkuu’s neighbor was kind enough to offer him. A surprisingly traditional Japanese meal for someone of Senkuu’s modern tastes. Tsukasa wasn’t capable enough in a kitchen to cook on his own, so he’d often eat prepared meals based upon his training regimen. It didn’t leave much room for flavor or delicacy.

Again, as if Senkuu was reading his mind…

“Cooking is just another form of science. Did you enjoy the meal?”

“It was delicious. You never cease to surprise me, Senkuu. Next thing I’ll hear is that you’ve prepared dessert.”

“Well it’s either that or me.”

Tsukasa lifted an eyebrow, not quite sure if he had heard what he did. The double take was probably very visible on his face, because Senkuu had a devilish grin on his face as he picked up their dirty dishes and took them over to the sink. Afterwards, Senkuu made his way to his room and motioned for the stunned Tsukasa to follow. Maybe it was the food or the way his teeth glistened, but Tsukasa found himself following Senkuu’s beckoning call. Getting up from his chair, he had taken strides to keep up with the scientist, the green hair already disappearing around the corner and into the darkened room. 

By the time Tsukasa had turned the corner, Senkuu was already in his room’s bathroom, the light shining through the door the only source of clarity at this moment in time. Senkuu’s silhouette was terribly visible behind the glass, though the boy’s features were muddled against the cloudy material. Senkuu’s voice could be heard behind the door.

“I’m taking a quick shower. Stay at the edge of my bed, will you?”

And so, Tsukasa sat at the edge of the bed and took several deep breaths, his chest rising and falling just as his anticipation and anxiousness rose and fell in tandem. The sound of water falling in the room next door was calming like rainfall in the countryside but enticing as he knew what remained behind the door and the events that would soon follow once the door opened. How did he end up in this situation? 

It wasn’t like Senkuu and Tsukasa spent a significant amount of time alone with each other. Rather, a majority of their time together was spent with Taiju and Yuzuriha, both of them kind of acting as a third and fourth wheel. In spite of everything, he couldn’t deny they had some unexplainable chemistry and he was far from being against getting to “that” point with his friend. He did find him incredibly attractive after all. Every so often, Tsukasa could feel a different kind of sensation coming from Senkuu when they were hanging out, but it was nothing more than a hunch.

So, the question stood then. How did he end up in this situation…?

The martial artist’s heart felt like it skipped a beat when the sound of water had ceased. Every moment felt like an eternity as Senkuu’s footsteps approached the door. Click - the sound of the door’s knob turning and releasing the only wall between the two men. Tsukasa gulped and he’d turned to face a nearly-nude Senkuu, the only thing covering him being a towel around his waist. The hair that normally stood on end was tamed by the weight of water, falling around his face and onto his shoulders. His body was dainty, but not at all out-of-shape. Slim, yet firm. Perhaps Tsukasa wasn’t giving Senkuu’s body a proper evaluation previously…

“Oh, good. You stayed. It would have been 10 billion percent embarrassing if I had come out of there and you were nowhere to be seen.”

Those words seemed playful, as if Senkuu actually knew from the beginning that Tsukasa was going to stay… More of Senkuu’s deviousness on the surface. The tense situation for Tsukasa did nothing to ease his nerves and he soon discovered that the tension was found in a particularly prominent part of his body. Another deep breath. It was strange being so out of his sense of normalcy. It was safe to say that he was quite fond of this side of the young scientist.

This became especially apparent when Senkuu had seemingly popped in front of him and was already pushing him down onto the bed. As strong as the World’s Strongest Primate was, he couldn’t resist the allure of this scientist. Groaning as his back landed against the bed, Senkuu was already straddling Tsukasa and pressing his surprisingly soft, bare ass against the tent of Tsukasa’s pants. Even the sensation of the clothed riding was staggering… what would it feel like if the pants were off…?

Senkuu was - as it seemed, as always - several steps ahead of the warrior and he had reached back to undo Tsukasa’s button and zipper, a thin cloth of stretched underwear being the final barrier. Senkuu grinned with a light pink on his cheeks and he leaned back against the strained fabric, pressing himself back against it and stroking up and down on it. Tsukasa groaned more deeply now, at the cusp of a growl. Tsukasa wasn’t sure if Senkuu could tell what was going through his mind at this point - or, rather, how empty his mind was.

It took all of his willpower to hold himself back from ripping off his own clothes and taking the scientist here and now. Or perhaps he made that all too clear because Senkuu had pushed off of his backward leaning and was now holding his chest against Tsukasa’s. Senkuu’s own shaft was pressed between them and there was a slight squeak of pleasure that came from the scientist’s lips as he had leaned forward.

Then there was the softest sensation of what was like a cloud of flesh against his lips. Tsukasa lost himself in the light, yet purposeful kiss by the green haired minx and their lips would part ever so slightly before pressure was reasserted and the wave of endorphins flooded his mind again. Tsukasa, even while they made out, felt the excitement of his shirt’s buttons being undone one by one under the sneaky and crafty hands of this genius.

It was only a few moments before Tsukasa felt Senkuu’s hardened member against his stomach and the smooth movements of Senku’s hips had Tsukasa’s dick stroking along Senkuu’s perineum while the scientist’s own dick was pressed and rubbing against Tsukasa’s abs. While Tsukasa’s mind had previously taken each moment as an eternity, his mind was now moving faster than it ever had before - though it was also conversely muddled with pleasure and lust. The warrior’s hands moved on their own to rest on Senkuu’s lower cheeks and he had spread them ever so gently before thrusting his hips forwards to rub against the scientist’s body on his own. What was heard next were words that Tsukasa heard before everything faded were a few that he would never forget for the rest of his life.

“C’mon Strongest Primate… take me…”

From there, Tsukasa found himself enjoying a particularly lubricated asshole. Not thinking about the fact that Senkuu was probably preparing for this while he was in the shower, Tsukasa guided his tip to the tight hole that - due to the lubrication - took him in like an arm into a sleeve. The pressure that was pushing on all sides was a taste of pleasure that Tsukasa didn’t know he could feel. His beastial instincts kicked in and he hadn’t even considered that, before this point, he was a virgin - and from Senkuu’s uncoordinated movements and enthusiasm - Tsukasa was under the impression that he was as well. Everything he was doing was driven by instinct.

Senkuu’s breath grew ragged in his ear and the sweet moans that left the scientist’s lips left Tsukasa stunned by just how lewd he could be. Senkuu was whispering under his breath, but Tsukasa could make out his name being spoken and he couldn’t stop himself from pumping his solid lust into Senkuu’s sweet sin.

“F- _fuck_ , Tsukasa… please don’t stop…”

His hip movements were rhythmic for a few moments, each pump like a fiery burst of passion before Tsukasa threw away his inhibitions and he began to pound hard and fast into Senkuu like the gladiator that he was. A hunter taking his prey. A victor partaking in his spoils. It being his first time, however, he wasn’t going to hold out for very long. 

“Ahh, you feel so good, Senkuu, I’m gonna-”

The sensations that overtook every muscle in his body drowned him in pleasure and the spasms that followed allowed him to claim the scientist.

His ejaculate flooded the tight asshole and served to elevate his sexual instincts beyond what he could have ever imagined. Senkuu let out a deep, lusty moan and he released his own orgasm onto their stomachs, a sickly stickiness covering them both in their sin and their love. Senkuu wrapped his arms around Tsukasa’s broad shoulders and looked up at him affectionately.

“You realize, there’s no way we’re ending it here… right, Tsukasa?

Tsukasa stopped thinking, his body moving on its own. Everything faded to black as their worlds - and bodies - were bathed in white.

**Author's Note:**

> Feel free to join the Dr. Stone shipping server! All ships are welcome!  
> We have lots of events scheduled (including gift exchanges), RP our fave ships, talk about the recent chapters, share headcanons, etc!
> 
>   
> [Click here!](https://discord.gg/fakzTPp)


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